波浪作用下底泥特性及其质量输移研究

发布时间：2018-01-26 05:47

本文关键词： 河口黏性泥沙幂律流模型流变特性临界起动质量输移速度　出处：《天津大学》2015年博士论文　论文类型：学位论文

【摘要】：河口海岸黏性泥沙的流变特性、运动特性及其与波浪之间的相互作用对于预测和解决岸滩冲刷、淤积以及岸线变形起重要作用,因而具有重要的研究价值和广泛的应用价值。本论文将天津大港黏性粉沙质淤泥作为研究对象,通过试验和理论研究,系统的探索黏性泥沙的流变特性和运动规律。此外,本论文就波浪与底泥之间的相互作用建立两层数学模型,对幂律流底泥的质量输移速度进行了理论研究。为了解黏性泥沙的流变特性,对不同密度的泥样进行静态流变试验。根据试验结果,讨论不同密度黏性泥流的剪切应力随剪切率的变化关系;分别采用幂律流模型和Bingham塑性体模型对流变曲线进行拟合,得到不同密度黏性泥流对应的流变参数,继而分析流变参数与密度之间的关系。此外,为了解细颗粒泥沙的絮凝特性,对四组不同浓度的泥浆进行静水沉降试验,观察黏性泥沙沉降过程,并讨论黏性泥沙浓度对静水沉降速度的影响。为了了解波浪作用下黏性泥沙的起动规律,配置不同密度黏性泥流,进行表面波浪作用下的黏性泥沙起动试验。记录黏性泥沙起动时的临界波高,继而计算不同密度黏性泥沙的临界起动速度和临界起动切应力;分别分析黏性泥沙的临界起动速度和临界起动切应力与黏性泥沙密度之间的关系,并拟合它们之间的关系式,结果证明波浪作用下黏性泥沙的起动规律符合延伸希尔兹曲线。结合流变试验结果,建立临界起动切应力与宾汉屈服应力之间的关系。此外,将起动试验得到的临界起动切应力与文献中的结果进行对比验证,发现结果基本一致。为了研究波浪作用下底泥的质量输移速度,本文基于Euler坐标系统,建立波浪与底泥相互作用的两层理论模型:假设上层为水体,下层底泥由幂律流模型描述;波浪运动由作用在自由水表面上的周期性压力荷载驱动。基于浅水波和小变形假设,采用一种摄动分析法将问题展开到二阶,以便得到平均Euler速度。对于得到的一阶和二阶问题,分别通过数值迭代法和改进的五对角追赶法进行求解。根据数值计算结果,分析下层幂律流流动指数对二维流场、界面波高以及底泥质量输移速度的影响。此外,当自由水表面周期性压力发生改变时,分析二维流场、界面波高和底泥质量输移速度的变化。
[Abstract]:The rheological characteristics, motion characteristics and wave interaction of viscous sediment in estuaries and coasts play an important role in predicting and solving shoreline erosion, siltation and shoreline deformation. Therefore, it has important research value and extensive application value. In this paper, the viscous silt of Tianjin Dagang is taken as the research object, through the experiment and theoretical research. The rheological characteristics and motion law of viscous sediment are systematically explored. In addition, a two-layer mathematical model for the interaction between waves and sediment is established in this paper. The mass transport velocity of power-law flow sediment is studied theoretically. In order to understand the rheological characteristics of viscous sediment, the static rheological tests of mud samples with different densities are carried out. The relationship between shear stress and shear rate of viscous mudflow with different density is discussed. The power law flow model and the Bingham plastic body model were used to fit the rheological curve, and the rheological parameters corresponding to the viscous mudflow with different densities were obtained, and the relationship between the rheological parameters and the density was analyzed. In order to understand the flocculation characteristics of fine sediment, four groups of mud with different concentrations were tested by static water sedimentation to observe the sedimentation process of viscous sediment. The influence of viscous sediment concentration on the settling velocity of hydrostatic water is discussed. In order to understand the starting rule of viscous sediment under wave action, different density viscous mud flows are arranged. The critical wave height of viscous sediment was recorded, and the critical starting velocity and shear stress of viscous sediment with different density were calculated. The relationship between critical incipient velocity and critical shear stress of viscous sediment and the density of viscous sediment is analyzed, and the relationship between them is fitted. The results show that the starting law of viscous sediment under wave action accords with the extended Shields curve, and the relationship between critical shear stress and Bingham yield stress is established in combination with the rheological test results. In order to study the mass transport velocity of sediment under wave action, the critical starting shear stress obtained from the starting test is compared with the results obtained in the literature, and it is found that the results are basically the same. Based on the Euler coordinate system, a two-layer theoretical model for the interaction between waves and sediment is established: the upper layer is assumed to be a water body, and the bottom sediment is described by a power-law flow model; The wave motion is driven by the periodic pressure load acting on the surface of free water. Based on the assumption of shallow water wave and small deformation, a perturbation analysis method is used to expand the problem to the second order. In order to get the average Euler velocity, the first and second order problems are solved by numerical iteration method and the improved five-diagonal chasing method, respectively. The influence of the lower power law flow index on the two-dimensional flow field, interfacial wave height and sediment mass transport velocity is analyzed. In addition, when the periodic pressure on the free water surface changes, the two-dimensional flow field is analyzed. The variation of interfacial wave height and sediment mass transport velocity.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TV148

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